1. Field of Invention
This invention pertains to method and apparatus for identifying media placed in an information storage drive, such as a magnetic tape drive, and particularly for identifying when a cleaning cartridge is inserted into a magnetic tape drive.
2. Prior Art and Other Considerations
Information storage drives, such as magnetic tape drives, generally have a supply spindle and a take-up spindle upon which are mounted a supply reel and a take-up reel, respectively, of a medium such as magnetic tape. In a forward mode of operation, the medium travels from the supply reel past one or more transducer heads to the take-up reel. The transducer heads generally write information on the medium or read information written on the medium.
In recent years, some types of information storage drives have been built to utilize magnetic tape cartridges. Examples of cartridge-utilizing drives are the 8 mm drives produced by Exabyte Corporation such as models EXB-8200 and EXB-8500. The cartridges utilized by these drives have magnetic recording tape extending between a supply reel and a take-up reel. When a cartridge is initially inserted into the drive, several actions occur. For example, the reels of the cartridge fit over respective spindles (or hubs) of the drive. A dual infra-red LED of the drive extends through a central aperture of the cartridge. Also, a front cover of the cartridge is opened to expose the medium. Ultimately, when the drive tape path is loaded, a portion of the medium extending between the reels is pulled out of the cartridge and wrapped around and a drum and tape guides. The drum either reads or writes helical tracks of information on the tape. Examples of helical scan magnetic recording technology are shown in U.S. Pat. Nos. 4,843,495; 4,835,638; 4,845,577; and, 5,068,757, all of which are incorporated herein by reference.
The magnetic tape extending between the supply and take-up reels of the aforedescribed cartridges have beginning of tape (BOT) and end of tape (EOT) leaders provided at the linear extremities thereof. The BOT and EOT leaders are transparent, whereas the remainder of the magnetic tape is opaque.
As mentioned above, a dual infra-red LED is centrally provided in the drive and extends into the interior of the cartridge upon insertion. The dual infrared LED directs infra-red light in a first direction toward a first window provided in the cartridge. The infra-red LED also directs light in a second direction (which is about 180.degree. opposite the first direction) toward a second window of the cartridge. The first window is aligned with a EOT photo transistor mounted in the deck, and the second tape window is likewise aligned with an BOT photo transistor in the deck.
Upon leaving the supply reel, the tape travels between the dual infra-red LED and the EOT photo transistor situated to receive light directed in the first direction. Before entering the take-up reel, the tape travels between the dual infra-red LED and the BOT photo transistor situated to receive light directed in the second direction. Each photo transistor conducts when a transparent leader of the tape is present between the LED and the photo transistor.
The transducer heads of drives become soiled by the magnetic media travelling therepast and must periodically be cleaned. To this end, specialized cleaning cartridges have been developed which are insertable into the drive in the same manner as magnetic tape cartridges, but which have a cleaning medium rather than magnetic tape medium extending from a supply reel to a take-up reel. The cleaning medium travels past the heads for removing debris which may have accumulated on the heads. In most cleaning cartridges, the amount of cleaning medium extending between the supply reel and the take-up reel is significantly less than the amount of magnetic tape provided in a standard tape cartridge, such as a 8 mm cartridge.
A drive must detect the presence of a cleaning cartridge inserted therein in order not to write on or attempt to read the cleaning medium. In this regard, in view of the lesser amount of cleaning medium provided in a cleaning cartridge, drives such as the models EXB-8200 and EXB-8500 referenced above heretofore attempted to ascertain the presence of a cleaning cartridge inserted therein by calculating the "area constant" of the medium in the cartridge. This calculation requires loading the medium in the tape path of the drive and advancing the medium a considerable distance from the supply reel to the take-up reel in order to determine the radii of the tape pack on each reel. If the "area constant" is in a predetermined relatively small range, the drive determines that the cartridge inserted therein is a cleaning cartridge.
The "area constant" calculation method requires that the length of medium in cleaning cartridges be held to tight tolerances. However, the sizes of cleaning cartridges are not necessarily standardized, with the result that some cleaning cartridges can be mistaken for data cartridges.
Moreover, the "area constant" method for identifying a cleaning cartridge requires a fairly consequential degree of media travel before the drive obtains enough sampling information to attempt the identification. This sampling requires time which otherwise could be put to more productive use.
Further, the "area constant" method often results in drum stall problems and repeated use at EOT.
Accordingly, it is an object of the present invention to provide an efficient and effective method and apparatus for identifying a cleaning cartridge inserted in a information storage drive.
An advantage of the present invention is the provision of method and apparatus for identifying the presence of a cleaning cartridge in an information storage drive without having to calculate the area constant of the medium in the cartridge.
Another advantage of the present invention is the provision of method and apparatus for identifying the presence of a cleaning cartridge in an information storage drive without having to load the tape path of the drive.
Yet another advantage of the present invention is the provision of method and apparatus for identifying the presence of a cleaning cartridge in an information storage drive by using pre-existing optical and electronic elements.
A further advantage of the present invention is the provision of method and apparatus which identifies a cleaning cartridge in an information storage drive regardless of the length of medium contained in the cartridge.